Primary and Secondary Mineral Analysis of Three Hawaiian Hydrothermally Altered Drill Cores as an Analog for Subsurface Aqueous Processes on Mars
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Authors
Sheevam, Pooja
Issue Date
2025
Type
Dissertation
Language
en_US
Keywords
Alteration , Drill Core , Geothermal , Infrared Spectroscopy
Alternative Title
Abstract
The Martian surface is predominantly basaltic, with extensive shield volcanoes formed over mantle hotspots. Evidence of water at and below the surface manifests in widespread detection of aqueous alteration of these basalts, with minerals ranging from phyllosilicates, sulfates, and carbonates. These detections are particularly noted in Noachian-aged terrains – which are considered the oldest, and lower lithological units. The presence of Al-phyllosilicates, Fe/Mg smectites, sulfates, and carbonates in stratigraphic sequences suggests multiple formation pathways, including in situ weathering, alteration of volcanic ash, or hydrothermal activity driven by volcanism or impact cratering. To accurately interpret these alteration signatures on Mars, it is crucial to establish well-characterized basaltic alteration sequences on Earth. Hawaiian basalts, formed in an oceanic hotspot setting, provide an ideal terrestrial analog for altered basaltic terrains on Mars.This study utilizes samples from three continuously cored deep subsurface exploration wells in Hawai‘i to investigate hydrothermal alteration in blind low to high temperature aqueous systems. These wells include: (1) PTA-2, a groundwater turned geothermal exploration well at the Pōhakuloa Training Area on the Island of Hawai‘i; (2) KMA-1, a groundwater exploration well at the Keāmuku Maneuver Area on the island of Hawai’i; and (3) HPF Well 10, a geothermal exploration well in the Pālāwai Basin on Lāna‘i Island. These wells were initially drilled for groundwater and geothermal assessments, and alteration mineralogy was not a primary focus of those studies. However, understanding alteration mineralogy is critical for constraining subsurface aqueous processes and fluid-rock interactions, which is not well documented outside the Kilauea East Rift Zone.
This dissertation presents a detailed alteration analysis using visible to short-wave and long infrared (VSWIR - LWIR) spectroscopy as the primary characterization tool. Each drill core revealed distinct alteration environments. PTA-2 and HPF Well 10, which had elevated subsurface temperatures, exhibited pervasive smectite group clays and zeolite alteration in vugs, fractures, and veins, with HPF Well 10 also containing abundant carbonate minerals. In contrast, KMA-1, the coolest well, displayed acid-sulfate alteration dominated by jarosite, alunite, and iron oxides.
These findings demonstrate that alteration mineralogy provides key insights into the history of subsurface aqueous alteration activity and can support observed structures controlling fluid flow. Such data can support exploration efforts and improve subsurface characterization in Hawaii. Furthermore, subsurface analog studies remain scarce in planetary science. This research advances our understanding of subsurface alteration processes on Mars by providing a comparative framework for interpreting secondary mineral bearing units in various volcanic settings. The opportunity to analyze drill cores from multiple geological contexts—ranging from a saddle region between two shield volcanoes to a system near a caldera center—further enhances our ability to assess localized hydrothermal alteration and its implications for planetary exploration.